Drafting machine



Dec. s; 1941. c. w. KEUFFEL' DRAFTING MACHINE 'Filed Aug. 19, 1939-INVENTOR CI/FZ H! KEV/7Z2 ATTORNEYS Tatentcl Dec. 23, 194i DRAFTINGMACHINE Carl W. Keuffel, Weehawken, N. J., assignor to Keuifel & EsserCompany, Hoboken, N. J., a corporation of New Jersey Application August19, 1939, Serial No. 290,962

13 Claims.

This invention relates generally to parallel motion drafting devices ofthe kind in which the several tools which the draftsman handles mostfrequently are embodied, in principle, in one unit to obviate thenecessity of a draftsman reaching about for a required tool and therebyenabling the draftsman to keep his attention concentrated directly uponthe drawing.

Drafting devices of this character are common in which adjacent ends oftwo arms are pivoted together, the free end of one arm being secured tothe remote side of a drafting board while the free end of the other armis provided with a head comprising a protractor and straight edges whichare in' fixed angular relation to move about the center of theprotractor as an axis. Where a drafting device of this character is usedupon a drawing board which is disposed in an inclined plane, the weightof the free arm and the head is likely to cause the angle between thetwo arms to become more obtuse and the head and straight edges will notremain at the desired place on the board unless the draftsman holds themat that point. A counterweight has heretofore been proposed as anexpedient to counterbalance the drafting device.

One object of the present invention is the provision of power storingdevices between the anchor and the arm pivoted thereto.

An important object of this invention is to provide a counterbalanceddrafting machine which will afford no obstruction to the movement of thescales and the like of the drafting machine.

A further object resides in providing a counterbalance ior a draftingmachine positioned below the plane of the drawing surface.

Another object of the invention is a drafting device of the characterdescribed wherein the counterbalancing devices are contained entirelywithin the anchor.

It is also an object of the invention to provide ready adjusting meansfor the tens-ion of spring means counterbalancing the drafting machine.

The invention also seeks counterbalancing devices which are practicalfrom the standpoint of ease and simplicity of manufacture and durabilityand practicability in use;

These and other objects of the invention and the means for theirattainment will be more apparent from the following detaileddescription, taken in connection with the accompanying drawingillustrating one embodiment by which the invention may be realized andin which:

Figure l is a view looking from above and showing the anchor ofadrafting device and a fragmentary portion of the arm pivoted thereto;

Figure 2 is a vertical sectional view showing the anchor of thisinvention; and

Figure 3 is a transverse sectional view taken in the plane indicated bythe line 3--3 of Figure 2 and looking in the direction of the arrows.

The anchor of this invention comprises an elongated housing 5 comprisinga straight wall 1 and an outwardly curved wall 8 defining a housing openat the bottom, the wall I having a plane surface 9 for engagement withthe remote side of a drafting table I I. The housing 5 is shown aselongated and is provided at each end with a bracket I3 in which isrotatably mounted a clamping screw I5 of any desired or common shape.Above the housing 5 and preferably centrally thereof is, conveniently, agenerally cylindrical or tubular portion l1, shown as comprising aportion l9, extending forwardly and intermediate the brackets l3,adapted to rest upon the table II and, with the clamping screws l5,clamp the anchor to the side of the table. Any convenient form ofadjusting device, such as indicated at 2 i, may be utilized to level theinstrument with respect to this table II.

The housing 5 is provided with a cylindrical surface 23 adapted toreceive anti-friction devices 25 for a pivot pin 21 on which is fixedlymounted the end 29 of one arm of the drafting device of this invention.A pulley 3| for the endless band 33 is formed with a downwardlyextending sleeve 35 which fits within the cylindrical portion ll of theanchor and serves, by means of screw 36, to secure the pulley 3| rigidlywith the anchor H,

the shaft 21 at its upper end being similarly positioned byanti-friction devices 25 seated in the fixed pulley 3|.

The counterbalancing means contemplated by this invention is illustratedas a leaf spring against which an eccentrically mounted member on theend of the shaft 21 bears. In the illustrated embodiment, a plate ordisc 31 is carried on the lower end of the shaft 21 and to the lowersurface of the disc 31 and in spaced relation to the axis of the shaftis secured a pin 39 to which a roller M is secured as by the screw 43.At one end of, and within the housing 5, and conveniently to the frontwall 1 thereof, is secured one end of a leaf spring 44, as by the screw45. If desired, this leaf spring 44 may be made up of a plurality ofleaves, as shown.

The other end of the leaf spring is movable in order to control thetension of the spring and cause it to bear against the roller 4|. In theillustrated embodiment, I provide the free end of the leaf spring 44with a pivoted adjusting nut 4'1 threaded on a screw 49 passing throughan aperture 5!! in the wall 8. The aperture 50 is preferably of adiameter greater than the diameter of the screw 49 and at its outer endterminates in a curvilinear or semi-spherical surface 5| against which acooperating or semi-spherical surface 53 of the knurled head 55 of thescrew bears.

Thus, by rotating the head of the screw, the nut 41 is caused to travelupwardly, say, toward the head until the spring is placed under thedesired degree of tension and would normally occupy a position such, forinstance, as that indicated in dotted lines in Figure 3. As the arm 35assumes a position substantially perpendicular to the wall 1, the roller4| places the spring under compression deflecting it, say, to .theposition shown in full lines in Figure 3. Since the center ofeccentricity of the pin 39 (and roller M) is on a line parallel to theaxis of the arm 29, the maximum force of the spring 44 (andmaximum'defiection) occurs when the arm 29 isperpendicular to the sideof the drawing board along which the wall 1 lies. The spring, however,exerts no effective force because it presses radially toward the axis ofpivot pin 27. As the arm 29 is moved in either direction from the justmentioned perpendicular position, the spring 44 exerts an efi'ectiveturning moment of 'a gradually decreasing force and gradually increasingmoment arm suficient to counterbalance the weight of the arm in allworking positions;

It will thus be seen that the entire counterbalancing device iscontained within an element of the anchor. The shape of the spring issuch that its maximum strength can be utilized and it is not likely tolose its resiliency or stretch. Moreover, the device, as a whole, iscompact as compared with the counterweighted counterbalancing devicesheretofore proposed. Should the spring weaken in any way or should theweight of the instrument be increased or decreased, the necessarychanges maybe made in the operative effect of the counterbalancingdevice by adjusting the tension on the spring in a simple and convenientmanner.

Various modifications will occur to those skilled in the art in thecomposition, configuration and disposition of the component elementsgoing to make up the invention as a Whole, as well'as in the varioususes to which the invention may be put, and no limitation is intended bythe phraseology of the foregoing description or illustrations in theaccompanying drawing except as indicated in the appended claims.

What is claimed is:

1. In a drafting machine, in combination, an anchor, a pivot pinrotatable thereon, an arm fixed to the pin to rotate therewith, a pulleyfixed to the anchor and within the arm, an eccentric carried by the pin,a leaf spring one end of which is secured to the anchor and intermediatethe ends of which the eccentric engages and means to adjust the positionof the other end of the spring.

2.In a drafting machine, in combination, an anchor, a pivot pinrotatable thereon, an arm fixed to the pin to rotate therewith, a pulleyfixed to the anchor and within the arm, aneccentric carried by the pin,a leaf spring one end of which is secured to the anchor and intermediatethe ends of which the eccentric engages and means to adjust the positionof the other end of the spring comprising an adjusting screw.

3. In a drafting machine, in combination, an

anchor, a pivot pin rotatable thereon, an arm fixed to the pin to rotatetherewith, a pulley fixed to the anchor and within the arm, an eccentriccarried by the pin, a leaf spring one end of which is secured to theanchor and intermediate the ends of which the eccentric engages andmeans to adjust the position of the other end of the spring comprising anut on the other end of the spring and an adjusting screw carried by theanchor and threaded in the nut.

4. In a drafting machine, in combination, an anchor, a pivot pinrotatable thereon, an arm fixed to the pin to rotate therewith, a pulleyfixed to the anchor and within the arm, an eccentric carried by the pin,a'leaf spring one end of which is secured to the anchor and intermediatethe ends of which the eccentric engages and means to adjust the positionof the other end of the spring comprising a nut on the other end of thespring and an adjusting screw passing through an oversize hole in theanchor and threaded in the nut, said anchor being formed with aspherical bearing surface andthe'h'ead' of the screw being formed with asurface complementary ther'etoj 5'. In a drafting machine, thecombination with means having a drawing surface,of at least'on'e arm andan anchor, a pivot pin by which the arm is pivotally mounted on theanchor, said'pivot pin extending below the drawing surface, 'a leafspring carried 'bythe anchor and an eccentric carried by the pina'ndengagingthe leaf spring intermediate its ends. 1

' 6. In a drafting machine, in combination, an anchor, a pivot pinrotatable thereon, an arm fixed to the pin to rotate therewith, a pulleyfixed to the anchor and within the arm, an eccentric carried by'the pinand a leaf spring one end'of which'is'secured to the anchor'andintermediate the ends of which the eccentric engages.

' 7. In a drafting machine, an anchor comprising a housing formed with atubular portion,a sleeve entering the tubular portionand formed with a'pulley, a pivot pin 'rotatably mounted within the sleeve and clampingmeans tosecure the housing to a drawing board. 1

8. In a drafting machine, an anchor comprising a housing formed with awall 'adapted't'o engage the side of a drawing board and a portion torest on the surface of the drawing board and a tubular portion, a sleeveentering'the tubular portion and formed with a pulley, meansto securethe sleeve in the housing, a pivot pin rotatably mounted within thesleeve, a drafting machine arm carried by the pivotpin and clampingscrew means carried by the housing andadap'ted to coact with the firstmentioned portion to engage the drawing board.

9. In a drafting machine, an anchor comprising a housing formed with atubular'portion, a sleeve entering the tubular portion and formed with apulley, means to secure the sleeve in the housing, :a pivot pinrotatably mounted within the sleeve, a drafting machine arm carried bythe pivot pin, counterbalanc'i'ng means between the pivot pin and thewall of the housing and clamping means tosecure the housing to adrawingboard.

10. In a drafting machine, in combination, an anchor, a pivot pinrotatable thereon, an arm carried by the pivot pin to turn therewith, aleaf spring carried by the anchor below the plane of a drawing surface,said pivot pin extending through the plane of the drawing surface,aneccentric carried by the pin at a point below the with a surface toengage plane of the drawingsurf'ace and engaging the spring and means'to adjust the tension of the spring.

11'; In a drafting machine, an anchor provided the top surface of adrawing board and having a downwardly extending member, an arm pivotedon said anchor above said anchor surface, eccentric means, means carriedby the arm and supporting the eccentric means below the plane of thesaid anchor surface and power storing means supported by said downwardlyextending portion disposed below the said anchor surface and engageableby the eccentric means to counterbalance the arm.

12. In a drafting machine, an anchor provided with a surface to engagethe top surface of a drawing board and having a downwardly extend ingmember, an arm pivoted on said anchor above said anchor surface,eccentric means, means carried by the arm and supporting the eccentricmeans below the plane of the said anchor surface and power storing meanssupported by said downwardly extending portion disposed below the saidanchor surface and engageable by the eccentric means which will exert noturning moment when the said arm is in one position and acounterbalancing moment when said arm is moved in either direction fromsaid one position.

13. In a drafting machine wherein at least one arm is movable over thedrawing surface of a drawing board, an anchor adapted to be removablysecured to the drawing board provided with a surface to engage thedrawing surface of a drawing board and having a downwardly extendingmember, a pivot pin rotatable on the anchor and on which the arm isfixed, said pivot pin extending through the plane of the said anchorsurface, power storing means, means supporting the power storing on saidanchor below the plane of said anchor surface and an eccentric carriedby the pin at a point thereon below the plane of said anchor surface andengaging the power storing means to counterbalance the arm.

CARL W. KEUFFEL.

